Agricultural vacuum conveyors for conveying granular material, such as grain, using a vacuum are well known. These vacuum conveyors allow the pickup of the granular material with a flexible hose that allows for considerable freedom of movement. A fan or air pump is used to establish a flow of air from the intake end of the hose through the vacuum conveyor to a discharge. An intake nozzle at the end of the hose is placed in the granular material, and the air being sucked into the intake end picks up and carries the granular material causing there to be a stream of mixed air and granular material that is carried up through the hose. From the hose, this granular material can enter the vacuum intake where it will eventually be deposited in an intake of the conveyor (such as an auger). When the granular material reaches the conveyor, the conveyor can carry the granular material up the length of the conveyor to be discharged into a bin, trailer, truck, etc.
When the intake end of the nozzle is placed in a pile of granular material, the flow of air entering the intake nozzle can be blocked by the granular material and if the suction created by the vacuum conveyor is not great enough to suck up this blockage, the vacuum conveyor could stall out. To address this, vents can be provided on the intake nozzle so that air can enter the nozzle and maintain an air flow entering the vacuum conveyor even if the end of the nozzle is filled with granular material. There are a number of variants of nozzles with these vents, but one version is shown in U.S. Pat. No. 6,979,152.
However, the ideal number and placement of vents is affected by the length of hose used with the vacuum conveyor and in most vacuum conveyors sections of hose can be added or removed depending on the distance between the vacuum conveyor and the granular material to be collected. This means that the vents used in a nozzle will be ideal for one hose length but not as good for others. Some nozzles, such as the one described in U.S. Pat. No. 6,979,152, provide a baffle or sleeve that allows the cross-sectional area of the vents to be varied thereby allowing an operator to restrict the flow of air through these vents, but these systems rely on the operators judgment and the restriction in the size of the vents can affect the air flow passing through these vents making the air flow react in unexpected and less efficient ways.